How many possible stereoisomers are there of the following heptose?

Question

Quizplus · Accepted Answer

The heptose has four chiral centers, which gives 2^4 = 16 possible stereoisomers. However, there are two meso compounds, which are achiral and thus do not have stereoisomers. Therefore, the total number of possible stereoisomers is 16 - 2 = 14. But we need to consider that D-glyceraldehyde and L-glyceraldehyde are enantiomers, so we need to divide by 2. Thus, the final answer is 14/2 = 7 pairs of enantiomers, which gives a total of 14 possible stereoisomers. The closest answer choice is C (32), which is double the correct answer because it does not take into account the meso compounds and counts each enantiomer pair separately.

How Many Possible Stereoisomers Are There of the Following Heptose